This eliminates weird lines:

```
PS>$global:?
True
```

This was the only affected invocation.

This should save 50 MB.

See: https://docs.python.org/3/using/windows.html

…eference`.

This uses the exact same `System.Security.Cryptography.RandomNumberGenerator` machinery:
https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/get-securerandom?view=powershell-7.4

It was added in PowerShell 7.4, released 2023-11-16:
https://learn.microsoft.com/en-us/powershell/scripting/whats-new/what-s-new-in-powershell-74?view=powershell-7.4

I had removed this environment variable technique in GH 3651, saying "The previous method stopped working.", but it clearly works here now. Let's keep both.

```
stl-lit.py: D:\GitHub\STL\llvm-project\llvm\utils\lit\lit\main.py:72: note: The test suite configuration requested an individual test timeout of 0 seconds but a timeout of 240 seconds was requested on the command line. Forcing timeout to be 240 seconds.
stl-lit.py: D:\GitHub\STL\llvm-project\llvm\utils\lit\lit\LitConfig.py:129: fatal: Setting a timeout per test not supported. Requires the Python psutil module but it could not be found. Try installing it via pip or via your operating system's package manager.
```

…ell 11.5.0.

`std.ixx` was explicitly including `<yvals_core.h>` for the workaround, which is no longer necessary.

VSO-1975579 "Standard Library Modules: fatal error C1116: unrecoverable error importing module 'std'.
Specialization of 'std::invoke_result_t' with arguments '_Fn, _Ty...'".

… (fixed) and LLVM-41915 (still active).

VSO-119526 "Multiple versions of special member function should be allowed" was fixed after 11 years.

LLVM-41915 "Implement CWG 1496" is still active, but implementing `is_trivial` with `__is_trivially_constructible(_Ty) && __is_trivially_copyable(_Ty)`
isn't a transparent workaround - it causes DevCom-1586179 VSO-1439353 "std::is_trivial incorrectly fails because of protected defaulted default constructor".
Let's just use the dedicated compiler builtin, and blame the compiler if it goes wrong - we've moved away from attempting to compensate for compiler deficiencies in type traits.

…ng), but (portably) trivially default constructible.